bb10006: cell & molecular biology
DESCRIPTION
BB10006: Cell & Molecular biology. Dr. MV Hejmadi Dr. JR Beeching (convenor) Prof. RJ Scott Prof. JMW Slack. Dr. Momna Hejmadi ([email protected]). Structure and function of nucleic acids Books (any of these) : - PowerPoint PPT PresentationTRANSCRIPT
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BB10006: Cell & Molecular biology
Dr. MV Hejmadi
Dr. JR Beeching (convenor)
Prof. RJ Scott
Prof. JMW Slack
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Dr. Momna Hejmadi ([email protected])
Structure and function of nucleic acids
Books (any of these):Any bioscience textbook will do but my
favourites are Biochemistry (3e) by D Voet & J VoetMolecular biology of the cell (4th ed) by Alberts et alEssential Cell Biology by Alberts et al
Key websites http://www.dnaftb.org/dnaftb/ http://www.dnai.org/lesson/go/2166/1994 http://molvis.sdsc.edu/dna/index.htm
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Outline of my lectures
Lecture 1. Nucleic acids – an introduction
Lecture 2. Properties and functions of nucleic
acids
Lecture 3. DNA replication
Lectures 4-6. Transcription and translation
Access to web lectures athttp://www.bath.ac.uk/bio-sci/hejmadi/teaching%202005-06.htm
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Lecture 1 - Outline How investigators pinpointed DNA as the genetic materialThe elegant Watson-Crick model of DNA structureForms of DNA (A, B, Z)
References: History, structure and forms of DNA
http://www.dnai.org/lesson/go/2166
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Timeline1869 F Miescher - nucleic acids
1928 F. Griffith - Transforming principle
http://www.dnai.org/lesson/go/2166/1994
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Discovery of transforming principle
1928 – Frederick Griffith – experiments with smooth (S) virulent
strain Streptococcus pneumoniae and rough (R) nonvirulent strain
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Griffith experiment
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Griffith experiment
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What is this transforming principle?
Bacterial transformation demonstrates transfer of genetic material
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Timeline1800’s F Miescher - nucleic acids
1928 F. Griffith - Transforming principle
Avery, McCleod & McCarty- Transforming principle is DNA
1944
http://www.dnai.org/lesson/go/2166/1994
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Avery, MacLeod, McCarty Experiment
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Avery, MacLeod, McCarty Experiment
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Timeline1800’s F Miescher - nucleic acids
1928 F. Griffith - Transforming principle
1949
Avery, McCleod & McCarty- Transforming principle is DNA
1944
Erwin Chargaff – base ratios
http://www.dnai.org/lesson/go/2166/1994
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E. Chargaff’s ratios
A = TC = G
A + G = C + T% GC constant for given species
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Timeline1800’s F Miescher - nucleic acids
1928 F. Griffith - Transforming principle
1952
Avery, McCleod & McCarty- Transforming principle is DNA
1944
Hershey-Chase ‘blender’ experiment
http://www.dnai.org/lesson/go/2166/1994
1949 Erwin Chargaff – base ratios
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Hershey and Chase experiments
1952 – Alfred Hershey and Martha Chase provide convincing evidence that DNA is genetic material
Waring blender experiment using T2 bacteriophage and bacteria
Radioactive labels 32P for DNA and 35S for protein
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Timeline1800’s F Miescher - nucleic acids
1928 F. Griffith - Transforming principle
1952
Avery, McCleod & McCarty- Transforming principle is DNA
1944
Hershey-Chase ‘blender’ experiment
1952 Erwin Chargaff – base ratios
1952 R Franklin & M Wilkins–DNA diffraction pattern
http://www.dnai.org/lesson/go/2166/1994
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X-ray diffraction patterns produced by DNA fibers – Rosalind Franklin and Maurice Wilkins
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Timeline1800’s F Miescher - nucleic acids
1928 F. Griffith - Transforming principle
1952
Avery, McCleod & McCarty- Transforming principle is DNA
1944
Hershey-Chase ‘blender’ experiment
1952 Erwin Chargaff – base ratios
1952 R Franklin & M Wilkins–DNA diffraction pattern
1953 J Watson and F Crick – DNA structure solved
http://www.dnai.org/lesson/go/2166/1994
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The Watson-Crick Model: DNA is a double helix
1951 – James Watson learns about x-ray diffraction pattern projected by DNA
Knowledge of the chemical structure of nucleotides (deoxyribose sugar, phosphate, and nitrogenous base)
Erwin Chargaff’s experiments demonstrate that ratio of A and T are 1:1, and G and C are 1:1
1953 – James Watson and Francis Crick propose their double helix model of DNA structure
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Human genome project
Public consortiumHeaded by F CollinsStarted in mid 80’sWorking draft completed
in 2001Final sequence 2003Nature: Feb 2001
Celera GenomicsHeaded by C VenterStarted in mid 90’sWorking draft completed
in 2001
Science: Feb 2001
Human genome = 3.3 X 10 9 base pairsNumber of genes = 26 – 32,000 genes
Goal: to sequence the entire human nuclear genome
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The human genomeThe human genome
Nuclear genome (3.2 Gbp) 24 types of chromosomes Y- 51Mb and chr1 -279Mbp
Mitochondrial genome
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DNA in forensicswhat can a single human hair tell
you?
nuclear DNAnuclear DNAHair rootHair root
mitochondrial DNAmitochondrial DNAHair shaftHair shaft
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Types of RNATypes of RNA
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Nucleotides
DNA RNA
Originally elucidated by Phoebus Levine and Alexander Todd in early 1950’s
2’-deoxy-D-ribose 2’-D-ribose
Made of 3 components1) 5 carbon sugar (pentose)2) nitrogenous base3) phosphate group
1) SUGARS
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2) NITROGENOUS BASES planar, aromatic, heterocyclic derivatives of purines/pyrimidines
adenine
uracil
thymine
cytosine
guanine
pyrimidines
purines
Note:Base carbons denoted as 1 etc Sugar carbons denoted as 1’ etc
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Nucleotide monomernucleotide = phosphate ester monomer of pentosedinucleotide - Dimer
Oligonucleotide – short polymer (<10)
Polynucleotide – long polymer (>10)
Nucleoside = monomer of sugar + base
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1) Phosphodiester bonds
5’ and 3’ links to pentose sugar
2) N-glycosidic bonds
Links nitrogenous base to C1’ pentose in beta configuration
5’ – 3’ polynucleotide linkages
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3’ end
5’ end 5’ – 3’ polarity
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Essential features of B-DNA
• Right twisting • Double stranded
helix• Anti-parallel • Bases on the
inside (Perpendicular to axis)
• Uniform diameter (~20A)
• Major and minor groove
• Complementary base pairing
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DNA conformations
Right-handed helix
intermediate planes of the
base pairs nearly perpendicular to the helix axis
tiny central axis wide + deep
major groove narrow + deep
minor groove
Right-handed helix
Widest planes of the
base pairs inclined to the helix axis
6A hole along helix axis
narrow + deep major groove
Wide + shallow minor groove
Left-handed helix
Narrowest planes of the
base pairs nearly perpendicular to the helix axis
no internal spaces
no major groove
narrow + deep minor groove
B-DNAB-DNAA- DNAA- DNA Z-DNAZ-DNA
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BB AA ZZ
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Structurally, purines (A and G) pair best with pyrimidines (T and C)
Thus, A pairs with T and G pairs with C, also explaining Chargaff’s ratios
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Problem
http://www.dnaftb.org/dnaftb/19/concept/index.html
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Maybe because RNA, not DNA, is prone to base-catalysed hydrolysis
Why has DNA evolved as the genetic material but not RNA?
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linear
human chromosomes
Double stranded DNA
Genetic material may be DNA
Single stranded DNA
circular
linear
circularProkaryotesMitochondriaChloroplastsSome viruses(pox viruses)
Parvovirus
adeno-associated viruses
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reoviruses
Double stranded RNA
Genetic material may be RNA
Single stranded RNA
Retroviruses like HIV
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RNA / DNA hybridse.g. during retroviral replication
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What is the base found in RNA but not DNA? ?
A) CytosineB) Uracil
C) Thymine D) Adenine E) Guanine
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What covalent bonds link nucleic acid monomers?
A) Carbon-Carbon double bondsB) Oxygen-Nitrogen Bonds
C) Carbon-Nitrogen bonds D) Hydrogen bonds
E) Phosphodiester bonds
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What sugar is used in in a DNA monomer?
A) 3'-deoxyribose
B) 5'-deoxyribose
C) 2'-deoxyribose
D) Glucose
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Each deoxyribonucleotide is composed of
A) 2'-deoxyribose sugar, Nitrogenous base, 5'- hydroxyl
B) 3'-deoxyribose sugar, Nitrogenous base, 5'- hydroxyl
C) 3'-deoxyribose sugar, Nitrogenous base, 5'- Phosphate
D) Ribose sugar, Nitrogenous base, 5'-hydroxylE) 2'-deoxyribose sugar, Nitrogenous base, 5'- phosphate